Frankly I don't believe it. The total area may be covered but I very much doubt that every lost path has been reported.
Neither do I.
What this exercise will show are the ways left off the Definitive Map, which the OS recorded in there editions between 1880 and 1949. Mainly because landowners had influence on Parish an County Councils and did not wish to follow the dictates of an Act of Parliament.
There are ways to infer from this unique record how people moved around the countryside due to the needs of the time. Also it is reasonable to suppose that they did this without the express permission of the freeholder, as many ways seem to cross boundaries of freehold.
What are the ways that have been lost between 1949 and 2020, base on the needs that have not been recognized, but have evolved with changing times and types of use.
Also in explaining the access network a past landowner leader described the network as made up of 'old ways to work'. In the 17th, 18th and 19th centuries the Grand houses set in landscaped Parkland were the primary employers in the countryside, yet the drives to these old places of work do not appear as Public Rights of Way, yet they are often set in excessive areas of privacy occupying many acres of our countryside and forcing the use of unsuitable roads.